Over drive (OD) is an important technology and is used to improve dynamic picture quality of a liquid crystal display (LCD) panel. Working principle of the OD is that a signal C is inserted between a signal A and a signal B when the signal A changes to the signal B, and LC molecules are driven to quickly deflect by a voltage difference between the signal A and the signal C. When one frame time of the signal C ends, a deflection angle of the LC molecules exactly accords with an angle requirement of the signal B. In a driving circuit of an LCD, a grey scale corresponds to a voltage of a signal, and the LCD panel automatically looks up a corresponding voltage of the signal C according to grey scale values of the signal A and the signal B. Most LCD panels currently use a color depth of 8-bit, and the signal A and the signal B have 256 grey scales, so capacity of an OD table is 256*256*8-bit (the 8-bit is storage space of the voltage of the signal C). If an OD table of a red pixel, an OD table of a green pixel, and an OD table of a blue pixel are different, the capacity of the OD table is 3*256*256*8-bit.
In most LCD driving circuits, space of a read-only memory (ROM) storing the OD table is not large, thus, an OD table of 17*17*8-bit is used. As shown in FIG. 1, in the OD table, the corresponding voltage of the signal C is added according to a grey scale value of the signal A and a grey scale value of the signal B, the grey scale values of the signal A is obtained from each of the 16 grey scales of the grey scale values of the signal A, and the grey scale value of the signal B is obtained from each of the 16 grey scales of the grey scale values of the signal B. An OD value of grey scales among each 16 grey scales is calculated by linear interpolation according to surrounding four voltages of the signal C, an equation of calculating the OD value is:
  Cmn  =            C      99        +                            M          -          208                16            *              (                              C            100                    -                      C            99                          )              +                            N          -          176                16            *                                 [                                    (                                                C                  82                                +                                                                            M                      -                      208                                        16                                    *                                      (                                                                  C                        83                                            -                                              C                        82                                                              )                                                              )                        -                          (                                                C                  99                                +                                                                            M                      -                      208                                        16                                    *                                      (                                                                  C                        100                                            -                                              C                        99                                                              )                                                              )                                ]                    
The above-mentioned method solves a problem of the storage of the OD table, but linear interpolation is not accurate, thus the OD table is also not accurate, which causes colored trailing of the dynamic picture.